Computer description of the C-stellarator ohmic heating discharges in hydrogen

Abstract

The behaviour of the ohmic heating discharges of hydrogen in the C-stellarator has been computed for a range of input parameters: ohmic heating currents, confining fields, initial gas densities, and recycling rates. The calculations were performed on a 7094 computer, by solving a set of coupled equations expressing particle densities, temperatures, emission of atomic and molecular light, etc. as functions of time in terms of known rate coefficients for ionization, excitation, dissociation, and charge exchange, and known relationships between electron temperature and the electrical conductivity, the particle loss rate, and the electron-ion collision rate. The calculated quantities are in reasonably good agreement with experimental data over the available range of parameters. The results show, inter alia, that it is immaterial (except for the emitted light) whether the strating gas, or the recycling, consists of 2H or H2; the ion temperatures achieved in the ohmic heating discharges are remarkably independent of the input parameters, and will not exceed similar 30 eV in a plasma of 5-cm radius at 36 kG. Extending the calculations to larger confining fields and discharge radii does not result in very substantial increase in particle temperature, without changing the assumed linear temperature dependence of the loss rate.